Method of making composite products from lignocellulosic materials

Abstract

This invention relates to a process for converting hemicellulose of lignocellulosic material into a thermoset, water-proof adhesive. In one embodiment of the invention the thermoset, water-proof adhesive is used for converting other components of the lignocellulosic material into composite products such as panel products, reconstituted lumber and moulded articles without the use of any other adhesive binders which are an essential part of the conventional dry process of manufacturing composite products, such as wood-based particleboard, waferboard, medium density fibreboard, et cetera.

I claim: 
     
       1. Process for converting hemicellulose of lignocellulosic material into a thermoset, water proof adhesive, comprising: (a) bringing lignocellulosic material in divided form and containing at least 10% hemicellulose, rapidly into contact with high pressure steam at a temperature high enough to release the hemicellose without carbonization thereof;   (b) maintaining the lignocellulosic material in contact with high pressure steam for a time sufficient only for the non-catalytic decomposition and hydrolization of hemicellulose into essentially low molecular weight, water soluble resin material selected from the group consisting of pentose and hexose sugars, sugar polymers, dehydrated carbohydrates, furfural products, organic acids and other minor decomposition products, with negligible carbonization of the hemicellulose and negligible degradation of cellulose;   (c) heating and pressing the water soluble resin materials thus produced in a concentrated form against a surface to be adhered thereto, at a temperature, time and pressure sufficient to polymerize, cross link and thermoset this material into a water proof adhesive adhering to the surface.   
     
     
       2. A process for converting hemicellulose of lignocellulosic material into a thermoset, water-proof adhesive, comprising; (a) bringing lignocellulosic material, in divided form and containing at least 10 percent hemicellulose, rapidly into contact with high pressure steam at a temperature T (°C.) in the range 160° C. to 260° C.,   (b) maintaining the lignocellulosic material in contact with the high pressure steam only for a time t (S) seconds in the range according to the formula t.sub.(S) -10 8 .5836-0.02801T(°C.)   whereby the temperature is high enough to release the hemicellulose, does not exceed the temperature for carbonization thereof, and, in combination with the limited treatment time t (S) is only capable of non-catalytic decomposition and hydrolyzation of hemicellulose into water soluble resin material selected from the group consisting of pentose and hexose sugars, sugar polymers, dehydrated carbohydrates, furfural products, organic acids and other minor decomposition products, with negligible degradation of cellulose having taken place,   (c) heating and pressing the water soluble resin material thus produced in a concentrated form, against a surface to be adhered thereto, at a temperature of at least 160° C. and for a sufficient time and pressure to polymerize, crosslink and thermoset this material into a waterproof adhesive adhering to the surface.   
     
     
       3. A process according to claim 1, wherein, (d) the lignocellulosic material, alone or in combination with other lignocellulosic material, in particle, fiber or flake form, containing the water soluble resin material from step (b) is concentrated, as soon as possible, by being dried to a low moisture content to prevent fermentation of the water soluble resin, then   (e) the dried lignocellulosic material, alone or in combination with other lignocellulosic material is formed into a mat, and then   (f) the mat is pressed in step (c) at a temperature in the range 160° C. to 250° C. to avoid charring the mat, and at a pressure and time sufficient, to first polymerize the water soluble resin into the said crosslinked polymeric substance, and thermoset the thus formed polymeric material into the water-proof adhesive, thereby bonding in situ the other components of the lignocellulosic material as the said surface to be ad ere to and forming a bonded, composite product.   
     
     
       4. A process according to claim 1, wherein the lignin portion of the lignocellulosic material is also decomposed and hydrolyzed into low molecular weight lignin and lignin products. 
     
     
       5. A process according to claim 1, wherein the hydrolyzed lignocellulosic material contains less then 30 percent by weight, of low molecular weigh t water solubles selected from the group consisting of sugars, sugar polymers, dehydrated carbohydrates, furfural products, organic acids, lignin, lignin products and other minor decomposition products. 
     
     
       6. A process according to claim 1, wherein the lignocellulosic material is brought into contact with the high pressure steam in a pressure vessel and, after maintaining the lignocellulosic material in contact with the high pressure steam for the time t (S) seconds, the steam pressure in the pressure vessel is released to atmospheric pressure with an explosive discharge to render the lignocellulosic material in fibrous and particulate form. 
     
     
       7. A process according to claim 1, wherein the lignocellulosic material is brought into contact with the high pressure steam in a pressure vessel and, after maintaining the lignocellulosic material in contact with the high pressure steam for the time t (S) seconds, the steam pressure in the pressure vessel is gradually brought to atmospheric pressure to retain the lignocellulosic material, other than the hemicullose and lignin, substantially in the original form. 
     
     
       8. A process according to claim 1, wherein the lignocellulosic material is brought into contact with the high pressure steam in a pressure vessel and, the steam pressure is maintained within the pressurized vessel while steam treated lignocellulosic material is continuously extruded from the pressure vessel to atmosphere in the time t (S) seconds. 
     
     
       9. A process according to claim 3, wherein the lignocellulosic material, after the high pressure steam treatment, is dried to a moisture content of less than 18 percent to avoid fermentation. 
     
     
       10. A process according to claim 1, wherein t e lignocellulosic material is at least one substance selected from the group consisting of stem, stalk, shrub, foliage, bark, root, shell, pod, nut, husk, fiber, straw, vine, grass, bamboo, reed and wood. 
     
     
       11. A process according to claim 1 or 3 wherein the lignocellulosic material in steps (a) and (e) is selected from the group consisting of particles, fibers, strands, wafers or flakes. 
     
     
       12. A process according to claim 2, wherein a portion of hemicellulose of the lignocellulosic material is removed from the lignocellulosic material before the lignocellulosic material is rapidly brought into contact with high pressure steam in step (a). 
     
     
       13. A process according to claim 1, wherein the lignocellulosic material of step (b) is expressed, or treated with water, to extract unpolymerized, water soluble resin material therefrom as an aqueous solution, water is evaporated from the aqueous solution to concentrate the water soluble resin material, and the concentrated, water soluble resin material is used in step (c). 
     
     
       14. A process according to claim 13, wherein the water is evaporated from the aqueous solution under vacuum. 
     
     
       15. A process of converting lignocellulosic materials into reconstituted composite products, comprising: (a) bringing lignocellulosic material in divided form and containing at least 10 percent hemicellulose rapidly into contact with high pressure steam at a temperature high enough to release the hemicellulose without carbonization thereof, for a time sufficient only for the non-catalytic decomposition and hydrolization of hemicellulose into essentially low molecular weight, water soluble resin material selected from the group consisting of pentose and hexose sugars, sugar polymers, dehydrated carbohydrates, furfural products, organic acids and otter minor decomposition products with negligible carbonization of the hemicellulose and negligible degradation of cellulose;   (b) immediately drying the lignocellulosic material to a water content of less than about 18%;   (c) shredding the lignocellulosic material to a fibrous state and forming it into a mat;   (d) pressing the said mat using heat and pressure to transform the decomposed and hydrolyzed products of hemicellulose to provide a thermoset adhesive bond and to yield a reconstituted composite product without charring the mat.   
     
     
       16. A process as in claim 15 in which the time in which the lignocellulosic material remains in contact with the high pressure stream is a time t (S) seconds in the range defined by the formula:   t.sub. S) =10.sup.8.5836-0.2801 T(°C.).     
     
     
       17. A process as in claim 16, in which the temperature of the high pressure steam is in the range 160° C. to 260° C. 
     
     
       18. A process as in claim 17 in which the mat is pressed at a temperature of about 160° C. to 250° C. and at a pressure and time sufficient to first polymerize the water soluble resin into a cross-linked polymeric substance, and thermoset the thus formed polymeric material into a water proof adhesive, thereby bonding in situ the otter components of the lignocellulosic material and forming a bonded composite product. 
     
     
       19. A process as in claim 15 in which the lignin portion of the lignocellulosic material is also decomposed and hydrolized into low molecular weight lignin and lignin products. 
     
     
       20. A process as in claim 15 in which the hydrolized lignocellulosic material contains less than 30% by weight of said essentially low molecular weight water soluble resin material. 
     
     
       21. A process for converting lignocellulosic material into a thermoset resin material, comprising: (a) bringing lignocellulosic material in divided form rapidly into contact with high pressure steam at a temperature high enough to decompose and hydrolyze hemicellulose contained in said lignocellulosic material without carbonization thereof;   (b) maintaining the lignocellulosic material in contact with high pressure steam for a time sufficient only for the decomposition and hydrolyzation of hemicellulose into low molecular weight, water soluble resin material selected from the group consisting of sugars, sugar polymers, furfural, dehydrated carbohydrate, organic acids and otter similar decomposition products, with negligible degradation of cellulose;   (c) separating out the water soluble resin material;   (d) bringing the remaining previously hydrolyzed lignocellulosic material in step (b) rapidly in contact with high pressure steam for a second time at a temperature high enough to decompose and hydrolyze cellulose without carbonization thereof;   (e) maintaining the previously hydrolyzed lignocellulosic material in contact with high pressure steam for a time sufficient for the decomposition and hydrolyzation of the cellulose into low molecular weight, water soluble resin material selected from the group consisting of hexose sugars, sugar polymers, hydroxymethyl furfural, organic acids and otter decomposition products;   (f) separating out the water soluble resin material from the hydrolyzed lignocellulosic material into the water soluble resin material and the hydrolyzed lignocellulosic residue;   (g) heating and pressing the water soluble material thus produced in steps (c) and (f) in concentrated form against a surface to be adhered thereto, at a temperature, pressure and for a time sufficient to polymerize, crosslink and thermoset this material into a waterproof adhesive bond adhering to the surface.   
     
     
       22. A process for converting hemicellulose of lignocellulosic material into a thermoset, water-proof resin adhesive, comprising: (a) bringing lignocellulosic material, in divided form rapidly into contact with high pressure steam at a temperature in the range of 150° C. to 260° C.;   (b) maintaining the lignocellulosic material in contact with the high pressure steam only for a time sufficient to decompose and hydrolyze hemicellulose into low molecular weight, water soluble resin material selected from the group consisting of pentose and hexose sugar, sugar polymers, dehydrated carbohydrate, furfural, organic acids and otter decomposition products, with negligible degradation of cellulose having taken place;   (c) heating and pressing the water soluble resin material thus produced in a concentrated form, against a surface to be adhered thereto, at a temperature of at least 160° C. and for a sufficient time and pressure to polymerize, crosslink and thermoset this material into a waterproof adhesive bond adhering to the surface.   
     
     
       23. A process for converting cellulose of lignocellulosic material into a thermoset, water-proof resin adhesive, comprising: (a) bringing lignocellulosic material, which as been treated with high pressure steam to decompose and hydrolyze hemicellulose and from which the water soluble resin material has been extracted, rapidly into contact with high pressure steam at a temperature in the range of 150° C. to 260° C.;   (b) maintaining the lignocellulosic material in contact with the high pressure steam for a time sufficient to decompose and hydrolyze cellulose into low molecular weight, water soluble resin material selected from the group consisting of hexose and pentose sugars, sugar polymers, dehydrated carbohydrate, furfural, organic acids and otter decomposition products;   (c) heating and pressing the water soluble resin material thus produced in a concentrated form, against a surface to be adhered thereto, at a temperature of at least 160° C. and for a sufficient time and pressure to polymerize, crosslink and thermoset this material into a water-proof adhesive bond adhering to the surface.   
     
     
       24. A process of converting lignocellulosic material into reconstituted composite products, comprising: (a) bringing lignocellulosic material in divided form rapidly in contact with high pressure steam at a temperature high enough to decompose and hydrolyze hemicellulose without carbonization thereof, for a time sufficient for the decomposition and hydrolyzation of hemicellulose into low molecular weight, water soluble resin material selected from the group consisting of pentose and hexose sugars, sugar polymers, furfural, dehydrated carbohydrate, organic acids and otter decomposition products with negligible degradation of cellulose;   (b) immediately drying and reducing, by, in either order, the lignocellulosic material into fiber or particulate to a moisture content of less than 18%;   (c) forming the lignocellulosic material alone or in combination with otter lignocellulosic material in subdivided form into a mat;   (d) pressing said mat, using heat and pressure to transform the decomposed and hydrolyzed products of hemicellulose to provide a thermoset adhesive bond to yield a reconstituted composite product without charring the mat.   
     
     
       25. A process according to claim 21, wherein, (h) the hydrolyzed lignocellulosic material, alone or in combination with otter lignocellulosic material, in particle, fiber or flake form, containing the water soluble resin material from steps (c) and (f) is concentrated, as soon as possible, by being dried to a low moisture content;   (i) the dried lignocellulosic material, alone or in combination with otter lignocellulosic material is formed into a mat, and then   (j) the mat is pressed at a high temperature to avoid charring the mat, at a pressure and for a time sufficient to first polymerize the water soluble resin material into the said crosslinked polymeric substance, and thermoset the thus formed polymeric material into the waterproof adhesive, t hereby bonding and bulking in situ the lignocellulosic material as the said surface to be adhered to and forming a bonded composite product.   
     
     
       26. A process according to claim 21, wherein the hydrolyzed lignocellulosic material containing 100% or less of water soluble resin material, in combination with otter lignocellulosic material, and in forms of particles, fibers or flakes from steps (b) and (e) is concentrated, as soon as possible, by being dried to a low moisture content, is formed into a mat, and then the mat is pressed at a temperature in the range of 160° C. to 250° C. to avoid charring the mat, and at a pressure and time sufficient to first polymerize the low molecular weight water soluble resin material into the said crosslinked, polymeric substance and thermoset the thus formed polymeric substance into the water-proof adhesive, t hereby bonding and bulking in situ the otter components of the lignocellulosic material as the said surface to be adhered to and forming a bonded composite product. 
     
     
       27. A process according to claim 21, wherein the water soluble resin material which is extracted from steps (c) and (f) and eluted with water from the decomposed and hydrolyzed lignocellulosic material, is processed into concentrated form. 
     
     
       28. A process according to claim 21, wherein the water soluble resin material obtained from the decomposition and hydrolization of hemicellulose and cellulose of the lignocellulosic material is used, separately or mixed together, as a thermosetting resin adhesive in liquid or solid form. 
     
     
       29. A process according to claim 21, wherein the water soluble resin materials derived from hemicellulose and cellulose of single or mixed species are used separately or in mixture. 
     
     
       30. A process according to claim 21, wherein the divided lignocellulosic material is mixed with an acidic catalyst in an amount of no more than 5% by weight before steam treatment to accelerate the thermal decomposition and hydrolyzation of hemicellulose and cellulose into water soluble resin material. 
     
     
       31. A process according to claim 21, wherein the lignocellulosic material is derived from forest and agricultural plants of woody or non-wood nature in a single or mixed species.